Inspection apparatus

1. A flake-inspection apparatus adapted to inspect a flow of flakes which consists at least in part of one or both of at least partially translucent flakes or at least partially clear flakes, comprising: a background reflector plate over which flakes are fed and adjacent which, in use, falls the flow of flakes, wherein the background reflector plate is a diffuse reflector; and a lighting unit comprising a single fixed, non-scanning light source for illuminating an elongate viewing field width-wise across the background reflector plate, the viewing field having a first width across the background reflector plate; and a camera unit for imaging a line which extends across the viewing field; wherein the background reflector plate, the light source and the camera unit are configured with respect to each other such that, in use, light travels: along a single-absorption light path of the light source-to-the background reflector plate-to-flake-to-the camera unit; and/or along a double-absorption light path of the light source-to-flake-to-the background reflector plate-to-flake-to-the camera unit; wherein the light source is formed of one or more light elements and has a second overall width which is less than 50% of the first width of the viewing field, whereby the second overall width of the light source is substantially narrower width-wise than the first width of the viewing field; and wherein the lighting unit has an illumination path, the camera unit has a detection path, and the illumination path and the detection path have an acute angular relation of less than 25 degrees, whereby double-absorption light paths are promoted in which transmission of light through flakes occurs twice, and, at wavelengths where flakes absorb light, an amount of light absorbed by flakes is doubled and contrast is greater.

2. The apparatus of claim 1 , wherein the second overall width of the light source is aligned in substantially parallel relation to the first width of the viewing field.

3. The apparatus of claim 1 , wherein the light source is an incandescent lamp, a halogen bulb, or a linear halogen bulb.

4. The apparatus of claim 1 , wherein the second overall width of the light source is less than 25% of the first width of the viewing field.

5. The apparatus of claim 1 , wherein the second width of the light source is less than 150 mm.

6. The apparatus of claim 1 , wherein the lighting unit further comprises a baffle which is disposed centrally and forwardly of the light source to render a brightness profile of illumination more uniform across the viewing field than in the absence of the baffle.

7. The apparatus of claim 1 , wherein the plurality of light elements which are arranged in spaced relation.

8. The apparatus of claim 7 , wherein the light source comprises first and second light elements which are spaced from each other by a distance of from 5% to 30% of the second overall width of the light source.

9. The apparatus of claim 1 , wherein the camera unit comprises a line scan camera which acquires line images from which at least one area image is formed.

10. A flake-inspection apparatus adapted to inspect a flow of flakes which consists at least in part of one or both of at least partially translucent flakes or at least partially clear flakes, comprising: a background reflector plate over which flakes are fed and adjacent which, in use, falls the flow of flakes, wherein the background reflector plate is a diffuse reflector; and a lighting unit comprising a single fixed, non-scanning light source for illuminating an elongate viewing field width-wise across the background reflector plate the viewing field having a first width across the background reflector plate; and a camera unit for imaging a line which extends across the viewing field; wherein the background reflector plate, the light source and the camera unit are configured with respect to each other such that, in use, light travels: along a single-absorption light path of the light source-to-the background reflector plate-to-flake-to-the camera unit; and/or along a double-absorption light path of the light source-to-flake-to-the background reflector plate-to-flake-to-the camera unit; wherein either: (a) the light source is formed of one or more light elements and has a second overall width, and the lighting unit further comprises a baffle which is disposed centrally and forwardly of the light source and has a third width across the background reflector plate of from 5% to 30% of the second overall width of the light source, or (b) the light source is formed of a plurality of light elements has a second overall width, and wherein the light elements are arranged in spaced relation and spaced by a distance of from 5% to 30% of the second overall width of the light source at a central portion of the light source.

11. The apparatus of claim 1 , wherein the background reflector plate is a white plate.

12. The apparatus of claim 1 , wherein the lighting unit further comprises a curved reflector which reflects the light from the light source to illuminate the viewing field.

13. The apparatus of claim 1 , wherein the flakes are plastic or polymeric flakes.

14. The apparatus of claim 10 , wherein the background reflector plate is a white plate.

15. The apparatus of claim 10 , wherein the lighting unit further comprises a curved reflector which reflects the light from the light source to illuminate the viewing field.

16. The apparatus of claim 10 , wherein the flakes are plastic or polymeric flakes.

17. The apparatus of claim 6 , wherein the baffle comprises an elongate element which extends substantially orthogonally to the first width of the viewing field.

18. The apparatus of claim 6 , wherein the baffle has a third width across the background reflector plate of from 5% to 30% of the second overall width of the light source.

19. The apparatus of claim 9 , wherein the line images acquired by the line scan camera are formed as a plurality of area images at different wavelengths.

20. The apparatus of claim 1 , wherein the illumination path and the detection path have an acute angular relation of less than 10 degrees.

21. The apparatus of claim 10 , wherein the baffle comprises an elongate element which extends substantially orthogonally to the first width of the viewing field.